18 

Copy I 



DEPARTMENT OF COMMERCE 
BUREAU OF FISHERIES 

HUGH M. SMITH, Commlwioner 



EXPERIMENTAL STUDY OF THE GROWTH AND 

MIGRATION OF FRESH-WATER 

MUSSELS 

By Frederick B, Isely 

Professor of Biology^ Central College^ 
Fayette^ Missouri 



APPENDIX m TO THE REPORT OF THE U. S. COMMISSIONER 
OF FISHERIES FOR I9I3 




Bureau of Fisheries Document No. 792 



WASHINGTON 

GOVERNMENT PRINTING OFFICE; 

1914 



^ 



\- 



DEPARTMENT OF COMMERCE 

BUREAU OF FISHERIES 

HUGH M. SMITH, Commissionet 



EXPERIMENTAL STUDY OF THE GROWTH AND 

MIGRATION OF FRESH-WATER 

MUSSELS 

By Frederick B, Isely 

Professor of Biology^ Central College, 
Fayette, Missouri 



APPENDIX III TO THE REPORT OF THE U. S. COMMISSIONER 
OF FISHERIES FOR 1913 




Bureau of Fisheries Document No. 792 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 

I9I4 



.Is 



D. OF W, 
JUL 28 1914 



\^ 



EXPERIMENTAL STUDY \m GROWTH AND 
MIGRATION OF FRESHlMR MUSSELS 



By pREDERICi'^ 

Professor of Biology,m -^^1^9^' 
Fayette, M 



Appendix III to the Report 
of Fisheries 



I Commissioner 



bbll 






m 



,'^'- 



m. — 



4 



CONTENTS. 



Introduction 5 

Plan of investigation 6 

Marking of specimens 6 

Field records 7 

Planting sites 7 

Planting of tagged specimens 7 

Shoofly Creek 7 

Chikaskia River 8 

Growth results 9 

Table 1. A year's growth in young Quadrulae 10 

Table 2. Two periods of growth, of one year and three months, respectively 11 

Table 3. Seasonal growth 12 

Tables 4-7. Rate of growth in different sizes of Quadrula undulata l3 

Table 8. Rate of growth by species 15 

Discussion of data 15 

Arrested -growth rings 17 

Migration 19 

Shoofly 19 

Chikaskia 20 

Discussion of migration data 21 

Economic bearing of experiments — Related problems 21 

Summary 22 

Literature cited 22 

Explanation of plates 23 



EXPERIMENTAL STUDY OF THE GROWTH AND 
MIGRATION OF FRESH-WATER MUSSELS. 



By Frederick B. Isely, 
Professor of Biology , Central College, Fayette, Missouri. 



INTRODUCTION. 

The growth lines of the Unionidse have long been considered by 
many observers as "annual rmgs," marking the yearly increase in the 
shell diameter. On the other hand, proof of the con'ectness of this 
assumption has been lacking, and not a few mvestigators have ques- 
tioned its validity. 

If the so-called annual rings do mark yearly additions, the rate 
of growth may readily be ascertained in many species by inspection; 
if, however, two or three of these hnes appear in one season, or 
prominent Imes appear only at in-egular yearly mtervals, the impor- 
tance of ''growth Imes" as definite mdicators of rate of growth loses 
much of its significance. 

The economic importance of fresh-water mussels has added a new 
stimulus to the study of the growth problem. Investigations ^ 
under direction of the Bureau of Fisheries durmg the past five years 
concerning various phases of and questions related to the problem 
of artificial propagation of the species valuable for use m the manufac- 
ture of pearl buttons, knife handles, etc., has promoted mquiry con- 
cerning the time required for an economic species to reach marketable 
size. 

Israel and Haas, among German investigators, have recently given 
the growth question some attention in connection with their extensive 
study of the fresh-water mussels of streams of Germany. In this 
country Lefevre, Curtis, and Coker^ have gathered experimental 
data concerning growth. 

In my study of the ecology of the Unionidae during the past five 
years, one of the perplexmg problems has been the rate of growth and 

a Various papers by Lefevre, Curtis, Coker, and other workers, in Bureau of Fisheries publications, the 
Journal of Experimental Zoology, and the Biological Bulletin for 1909, 1910, 1911, and 1912. 

b Through the kindness of Dr. Coker, I have been permitted to read in manuscript the results of his 
experiments and observations. . 

5 



6 GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 

the age question. After carrying on experimental work for some time 
on my own initiative, I was given opportunity in 1910 to undertake 
the work on a larger scale under the direction of the Commissioner of 
Fisheries. 

PLAN OF INVESTIGATION. 

In the experiments to be undertaken I proposed to ascertain the 
rate of growth, to mquire into the meanmg of growth Imes, to inves- 
tigate the relation of age, maximum size, etc., and, as a secondary 
problem, to gather data concerning migration. The plan of work 
was, in brief, to collect a thousand specimens of as many species and 
sizes as could be secured in. the region where the work was carried on ; 
in some way mark them individually, weigh, measure, and make any 
other necessary records; and then return them to their usual habitat 
and at suitable intervals reclaim, weigh, and measure again. 

To carry out this work, two questions of method had to be solved: 
(1) The marking of specimens and (2) the reclaiming of them. 

MARKING OF SPECIMENS. 

In 1909 I experimented with two ways of marking: One was to 
scratch a symbol (pi. i, H), as a Roman numeral, on the sheU, and 
in this way identify it for future records; the second method was to 
fasten a serial-numbered tag to the shell and keep records by these 
numbers. In the final work both methods were used, the former for 
light shells, the latter for heavy ones. 

The method of marking a shell by scratching a number on it is 
simple enough, as a mark cut through the epidermis of a mussel 
valve will be carried indefinitely. To get a satisfactory series for 
a large number of specimens, however, is difficult. 

The tagging with serial numbers seemed to me to be more exact. 
For this method I used brass tags about the size of a dime and 
fastened them to the specimens with a light copper wire passed 
through a small hole made in the posterior edge of the valve. The 
hole in the valve was made with a very fine button-eye drill about 
2 millimeters from the posterior edge of the shell (pi. i, ii, and iii). 
To hold the button-eye drill, a geared hand drill was used, and only a 
few seconds were needed to drill a hole even in a thick shell. By 
making a little hook on the wire it could be passed through the hole 
and out between the valves, usually without much difficulty. In 
large specimens it was found that the work of tagging could be more 
readily accomplished by wedging the valves open slightly before 
inserting the wire. A slight injury to the animal often resulted 
from the fact that the mantle was not sufficiently drawn back to 
avoid the drill point. While the irritation at the moment was 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 7 

doubtless severe, the ultimate effect upon the animal's future growth 
and activity was insignificant (p. 19). 

FIELD RECORDS. 

A tabular record was kept of all specimens tagged. The weights 
were taken in grams, a Harvard trip balance being used; the measure- 
ments, length, height, and breadth in millimeters with a steel 
caliper. The field record form, kept in duplicate, was ruled in 
columns with headings for number, weight, length, height, breadth, 
species, and remarks. 

PLANTING SITES. 

In most cases, after tagging and taking records, the mussels were 
placed directly back in their original habitats, but in some instances 
transplanting from river to creek or from pond to river was practiced. 

Four different sites were selected for planting: One on Shoofly 
Creek, on the Corn farm in the north end of Kay County, Okla.; 
two on the Chikaskia River, on the Brewer and Esch farms near 
Tonkawa, Okla.; and a pond site on the Browne farm near Autwine. 
As the pond dried up, due to the unusual drought of 1910, this series 
does not figure in the results. 

The Chikaskia River is a small, clear-water, sandy stream. The 
sand is coarse, and frequently there are stretches of gravel and 
occasionally mud banks and small, mud-bottomed side channels. 
In certain portions of the Chikaskia, Unionidse are abundant. 

Shoofly Creek is a tributary of the Chikaskia. In very dry weather 
the water stops flowing over the shallow, gravelly stretches; but 
the ponded sections, often a mile in length and -with water 2 to 6 
feet deep, have a constant water supply. In certain of these ponded 
portions mussels are fairly abundant. 

PLANTING OF TAGGED SPECIMENS. 

In all, about 900 specimens were tagged, weighed, measured, and 
listed for future observation. For convenience in further dis- 
cussion these specimens may be grouped into seven lots. 

SHOOFLY CREEK. 

Shoofly, lot A, 140 specimens, and lot B, 80 specimens. — Nearly 
all of these were Qitadrula undulata (three-ridge) and were taken 
from the direct site where they were planted after tagging. All 
of the Q. undulata (three-ridge) secured in the Shoofly were large; 
out of some 500 specimens handled in two days, only 4 weighed 
under 200 grams. 

20225°— 14— 2 



8 GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 

Shoofly, lot C. — Twenty-two specimens of Anodonta grandis (floater) 
were planted in a mud bank similar to the environment selected 
by this species in this creek. 

Shoofly, lot D. — As already indicated, the Shoofly species were 
mostly undulata, with a few grandis, and all were large. In order 
to get a larger number of species and smaller specimens, I collected 
168 mussels in the Chikaskia and planted them in the Shoofly. In 
this lot, Q. undulata (three-ridge), Q. lachrymosa (maple-leaf), 
Q. pustulosa (warty-back, pimple-back), and Q. ruhiginosa were 
represented by fairly good numbers, and nearly all of the specimens 
were under 200 grams in weight. It should be stated here that a 
few specimens of all of the QuadrulaB were found native of the Shoofly, 
and in addition to these, Lampsilis gracilis (paper-shell), Lampsilis 
anodontoides (yellow sand-shell), Symphynota complanata (heel- 
splitter), and Anodonta imhecilis were found. Not counting grandis 
(floater), the ratio would be 25 undulata (three-ridge) to one of 
another species. This, however, is not unusual in dominance of 
species in certain streams. 

In planting specimens, the bottom was cleared of the original 
occupants and the tagged specimens were put in their places. For 
example, for lot D, an area of bottom about 12 feet in diameter 
was cleared and the Chikaskia specimens spread out on the cleared 
bottom. The Shoofly bottom, where the sites were located, is made 
up of a mixture of broken blue shale, coarse sand, and mud. The 
water is still and cloudy and from 2 to 5 feet deep. The specimens 
were planted in water about 3^ feet deep. Results that follow 
indicate that the above is a favorable type of habitat for the species 
used. 

As already indicated, the specimens were free in the stream; no 
obstruction of any kind was placed in their way, nor any effort made 
to confine them. The planting operation consisted in turning them 
out of a sack and spreading them around on the stream floor. In 24 
hours after planting it was noticed that most of the specimens had 
righted themselves and were stuck in the bottom, foot end down, but 
seldom was a Quadrula found with the foot extended. 

The Shoofly specimens, lots A, B, C, and D, were tagged, weighed, 
etc., June 1.3 to 16, 1910 ; reclaimed and first checked over in part June 
14 and 15, 1911 ; and a second time some wei'e reclaimed and checked 

over September 19, 1911. 

«■ 

CHIKASKIA RIVER. 

In the Chikaskia two lots were planted. These were inclosed with 
a wire netting, as I was a little doubtful in regard to reclaiming free 
Unionidse in the Chikaskia. 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 9 

Chikaslcia, lot E. — On the Brewer farm were planted 120 speci- 
mens of various sizes of Quadrul^, and a few representatives of the 
other species mentioned for the Shoofly, with the addition of a few 
specimens of Lampsilis purpuratus and Tritogonia tuherculata (buck- 
horn, pistol-grip). The inclosure consisted of a triangular pen made 
of 3-foot, 1-inch mesh mre netting, run out from the bank and back 
again, 40 feet of netting being used in its construction. The bottom 
was a mud bank along the side and medium coarse sand farther out. 
The water was from 2 inches to 3 feet in depth, a portion of the main 
channel running across the lower end. The specimens were collected 
in part from the immediate vicinity of the inclosure, but, as they were 
by no means mmierous in this portion of the river, about 90 of the 
120 mussels were secured a mile farther down the stream. Lot E 
specimens were planted, weighed, etc., June 23 and 24, 1910, and 
checked over in part September 26, 1910, and June 22, 1911. 

Chikaslcia, lot F. — The second planting in the Chikaskia was on the 
Esch farm, and consisted of 330 specimens, collected mostly from the 
immediate vicinity, as the mussels in this portion of the river were 
abundant. The range of size was good, although really small speci- 
mens were rare in 1910. The species were about the same as noted 
under lot D, mostly Quadrulse, as these are the only common species 
in this stream. Fifty specimens of TJnio tetralasmus , a pond form 
never found in the Chikaskia, were placed in the Esch inclosure. Tliis 
pen was made by fencing across a side channel formed by a long bar. 
The channel was 40 yards long and from 4 to 6 yards wide. The 
bottom was mostly coarse sand. At the time of its construction 
there was a regular flow of water through the channel, the depth of 
water varying from a few inches to 3 feet. Lot F mussels were planted 
June 23 to 28, 1910; examined and rechecked in part September 26, 
1910, April 11, 1911, and June 20 and 21, 1911. 

GROWTH RESULTS. 

In discussing experiments and results, we will first consider growth, 
and second, migration (p. 19). 

The results have shown that much could have been learned from 
a smaller number of specimens. It was not known, however, that we 
should be able to reclaim so large a per cent of the specimens first 
planted. Then, too, it was necessary to guard against loss by acci- 
dents, such as changes in course of streams, drifting sand, drying up 
of water, and other possible environmental changes. The Shoofly 
specimens were absolutely unmolested; only three dead specimens 
were found in the whole lot, and these had all started to grow, showing 
that the tagging certainly had no bad effects. The Chikaskia speci- 
mens suffered somewhat from all of the hostile environmental factors 



10 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 



mentioned above; and, further, some were lost to the small boy inter- 
ested in collecting brass tags. 

On the whole, however, the specimens were reclaimed in such large 
numbers that all of the material could not be worked over for records 
in the time availal:)le when the rechecking and reclaiming was done. 

In rechecking material as many specimens were handled as time 
would permit. As small specimens were few in number, these were 
always rechecked and care was taken to include representatives of all 
species. Aside from these influences in selection, specimens were 
rechecked as found. The left-over material was returned to the 
stream when it could not be handled. Where a lot was checked over 
several times, as lot F, naturally the ones worked over the first time 
they were reclaimed, September 26, 1910, were again followed up in 
subsequent work. 

Far more data were gathered than can be included in this paper. 
In the tables given below I have stated the reasons for selecting the 
data presented. Nearly all the material used is selected from lots 
D and F, as the latter was more available for frequent recheckings, 
and lot D of the Shoofly material represented a larger number of 
species and more range as to size. 

Table 1. — -A Year's Growth in Young Quadrul^e from Lot D. 
[Note. — All starred numbers in tables represent specimens shown in plate figures.] 



Speci- 


Species. 


Weight. 


Length. 


Height. 


Breadth. 


men 
No.o 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


323* 
319 


Q. undulata (three-ridge). . . 
. . . .do 


Grams. 
20 
49.5 
66 
22.5 
26 
80 
52 
60 
104 

10 
54 
67 


Grams. 
43 
77 

102 
47 
53 

112 
65 
76 

115 

20 
63 
77 


Mm. 
45 
64 
70 
45 
45 
67 
64 
64 
76 

30 
56 
64 


Mm. 
62 
75 

80.5 
56 
59 
76 

68.5 
69 
79 

37 
58 
65 


Mm. 
31 
42 
46 
35 
36 
55 
48 
50 
60 

25 
45 
52 


Mm. 
42 
50 
51 
45 
46 
60 
50 
52 
65 

30 
46 
53 


Mm. 
17 
24 
27 
19 
20 
29 
26 
26 
32 

15 
28 
29 


Mm. 
23 
27 


341 


do 


31 


158* 
149* 


Q. lachrymosa (maple-leaf), 
do 


25 

25.5 


159 


do.. 


33.5 


368 


Q rubiginosa 


27 


351 


do . 


28 


353 


.do 


33.5 


349* 


Q. pustulosa (warty-back or 


20 


375 


do . 


29 


383 


(Jo 


30 









AVERAGE GAIN AND PER CENT OF AGGREGATE GAIN FOR EACH SPECIES. 



Species. 


Weight. 


Length. 


Height. 


Breadth. 




Grams. 
28.8 
27.8 
13.3 
9.6 


Perct. 
63 
64 
18 
22 


Mm. 

12.8 

11 
4.1 
3.3 


Per ct. 
21 
21 

6.1 

6 


Mm. 
8 

8.3 
3 
2.3 


Per ct. 

20 

19 
5.6 
5.7 


Mm. 
4.3 
5.3 
1.5 
2 


Per ct. 
19 




23 




5.3 




9.7 







a Specimens listed in all tables according to size for each species. 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 



11 



The foregoing tables relate to Unionidse from lot D (p. 8) that 
were planted June 15 and 16, 1910, and reclaimed June 15 and 16, 
1911. In the figures given, the first series under each number is the 
initial record, the second series the record a year later. These 
specimens show manner and extent of growth in one year's time for 
four species. They were killed at the time of reclaiming, and are 
preserved for future study should anyone wish to examme them. 
It can be seen at a glance that undulata (three-ridge) and lachrymosa 
(maple-leaf) are rapid growers m comparison with pustulosa (warty- 
back, pimple-back) and ruhiginosa. Further averages and per- 
centages are worked out for each species listed in table 1 and later 
tables on page 8. 

Table 2. — Two Periods of Growth, op One Year and of Three Months, 
Respectively, in Specimens Taken prom Lot D. 

[Note. — Starred numbers represent specimens shown in plate figures.] 



men 
No. 



135 

165 
146 
168 
283 

317 
329 
306 
171 
166 
307 
322 
163 
374 



363 
384 

377 
358 
355* 
371 



Species. 



Weight. 



June 
1910. 



Q. laehrymosa (ma- 
ple-leaf) 

do 

--..do 

--..do 

Q. undulata (three- 
ridge) 

....do 

....do 

....do 

....do 

....do 

....do 

....do 

....do 

Q. pustulosa (war- 
ty-back, pimple- 
back).... 

....do 

....do 

....do 

do 

Q. rubiginosao 

do 



Gms. 

92.5 
152 
164 
166 

95 
120 
125 
140 
145 
166 
183 
185.5 
200 



June, 
1911. 



Gms. 
124 
182 
216 
185 

132 
147 
149 
164 
175 
192 
217 
207 
226 



45 
73 
102 
107 
145 
75 
97 



Sept. 
1911. 



Gms. 
142 
194 
237 
197 

150 
162 
159 
176 
190 
214 
230 
220 
236 



50 
80 
112 
114 
152 
84 
104 



Length. 



June, 
1910, 



Mm. 
70 
93 
82 
93 

72 
83 
85 
90 
88 
92 
98 
93 



June, 
1911 



Mm. 
76 
96 



83 



96 
94 
97 

102 
97 

102 



Sept. 
1911. 



Mm. 
81 
97 
94 



92 

90 
100 

97 
102 
105 

99 
104.5 



57 

59.5 

66 

85 

90 

70 

80 



Height. 



June 
1910. 



Mm. 
57 
57 
68 
57 

46 
51 

55 
56 
52 
56 
64 
00 
58 



June, 
1911. 



Mm. 
63 
61 
70 
61 

51 

56 
60 
60 
55 



Sept. 
1911. 



Mm. 

66.5 

63 

72 

63 

56 
61 

62 
62 
58 



Breadth. 



June, 
1910. 



Mm. 
32 
37 
41 
37 

34 
34 
34 
35 
37 
38 
35 
41 
42 



June, 
1911. 



Mm. 

36 

39 

4.3.5 

39 

38 
37 
37 
37 
39 
40 
37 
42 
43 



Sept., 
1911. 



Mm. 
37.5 
40 
45 
40 

39 

38 

38 

38 

39.5 

41 

38 

42.5 

44 



27 

32 

36.5 

33 

35.5 

31 

33 



a It should be noted that five of the specimens for the two last species were more nearly mature for these 
species than the specimens of undulata (three-ridge) and laehrymosa (maple-leaf). 

The specimens shown in the preceding table were planted June 15 
and 16, 1910, and were reclaimed June 15 and 16, 1911, put back in 
the stream, and reclaimed September 9, 1911. All of the specimens 
of lot D that were reclaimed twice, measured, and weighed, are 
shown in table 2. 

In the figures given above, the first is the initial record, the second 
the record one year later, and the third a three months' summer 
record (June 15 and 16 to Sept. 9, 1911). 

Table 2 simply adds to the data of table 1 in regard to annual 
growth, growth of species, etc. It adds the fact of seasonal growth, 



12 



GEOWTH AND MIGRATION OF FEESH-WATER MUSSELS. 



and gives data for comparison of yearly growth and summer months. 
The average yearly growth for 20 specimens shown in table 2, as well 
as the growth for three summer months (85 days) is shown below : 





Weight. 


Length. 


Height. 


Breadth. 


Average gain for one year, 1910-11 

Average gain for three months, 1911 6 


Grams. 
23.2 
12.1 


Per cent.a 
18 
8.2 


Mm. 
4.2 
2.9 


Per cent.a 
5.2 
3.4 


Mm. 
3 
2.4 


Mm. 
2 
1 



a Per cent of aggregate gain. 

b It should be noted in this comparison that the 1910 and 1911 summer months were different in weaf^^r 
conditions. During 1910 there were no rains heavy enough to raise the creek and wash out the food sup- 
ply of micro-organisms, while in 191 1 there were two periods of high water, one in July and one in August. 

Per cent of gain gives a truer basis for this kind of comparison 
than the average net gain. The lack of conformity in the height 
averages, when compared with other measurements, is doubtless due 
to error on account of the great difficulty in getting this dimension 
in rapid field measurements because of the circular ventral margins 

of these species. 

Table 3. — Seasonal Growth. 



Speci- 


Species. 


Weight. 


Length. 


men 
No. 


June, 
1910. 


Sept., 
1910. 


Apr., 
1911. 


June, 
1911. 


June, 
1910. 


Sept., 
1910. 


Apr., 
1911. 


June, 
1911. 


594 
734 


Q. undulata (three-ridge). . . 
do 


Grams. 
210 
255 
261 
290 
104 
105 
154 
160 
163.5 
164 
187 

91 
141 

148 


Grams. 
222 
269 
273 
305 
116 
115 
167 
173 
174 
180 
195 

98 
146 
154 


Grams. 
222 
271 
272 
305 
114 
117 . 
167 
171 
176 
179 
200 

98 

146. 5 
156 


Grams. 
225 
270 

277 
305 
116 
123 
172 
180 
182 
180 
200 

99 

147 
156 


Mm. 
102 
116 
110 
118 
76 
66 
84 
86 
84 
86 
90 

64 

84 
84 


Mm. 

104 

122 

112 

125 

76 

67 

86 

88 

86 

89 

91.5 

64.5 

86 
86 


Mm. 

104 

122 

112 

125 

76.5 

68 

86 

88 

86 

89 

91.5 

64.5 

86 

80 


Mm. 
104 
122-f- 


678 


do.. 


112 


573 
644 
753 


do 

Q. lachrymosa (maple-leaf), 
do 


125 

77 
70 


665 


do 


86-1- 
89 


660 


do;:..:::.: 


687 


.. do 


86.5 


694 


.... do 


90 


622 


do 


91.5 


617 


Q. pustulosa (warty-back, 
pimple-back) 


64.5 


689 




86 


721 


do 


86 









While table 2 has given some good data concerning seasonal 
growth, table 3 gives more detail and permits a more exact location 
of the growth periods. Table 3 specimens are from lot F, Chikaskia 
River. These specimens were checked up, approximately, at the 
third, ninth, and twelfth months that they were under observation, 
and the results are shown by successive records. The initial records 
were taken June 23-28, 1910; second, September 26, 1910; third, 
April 11, 1911; and fourth, June 20, 1911. Only the weight « and 
length records appear in this table. The average gain for the dif- 
ferent periods we find to be as follows: 

a Some observers report weight measurements subject to a great deal of variation. In this investigation 
I have always kept tlie specimens out of water for short intervals and always under cover. Under these 
conditions I have found weight measures very satisfactory and stable under repeated reweighings. 



GEOWTH AND MIGKATION OF FRESH-WATER MUSSELS. 



13 



Weight. 



Length. 



June 28 to Sept. 26, 1910 
Sept. 26 to Apr. 11, 1911 
Apr. 11 to June 20, 1911. 



Orams. 


Mm. 


10.9 


2.4 


.5 


.1 


2.5 


.3 



For comparison with these averages we have the results from 
lot E, which I have not tabulated, for 14 specimens: 7 lachrymosa 
(maple-leaf); 4 undulata (three-ridge); and 3 pustulosa (warty-back, 
pimple-back). In this case the April reclaiming was not done. 



Time. 



June 23 to Sept. 26, 1910. 
Sept. 26 to June 23, 1911. 



Weight. 



Grams. 
9.1 
5.4 



Length. 



Mm. 



LO 
.55 



The second period shows a gain in the growth for lot E over lot F. 
The explanation is one of food and possibly oxygen, and appears 
later (p. 24) under the discussion of migration. 

The following four tables show proportional rate of growth, at 
different ages, of a single species, Q. undulata (three-ridge). The 
fact that lot D mussels were transplanted (p. 5) brings in an additional 
factor (footnote, p. 23), but I am not sure that this is material. In 
making these comparisons weight and length are used. 

Table 4. — Increase in One Year op Specimens prom Lot D, Weighing Less 

THAN 100 Grams. 





Weight. 


Length. 


Specimen No. 


Weight. 


Length. 


Specimen No. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


323 


Grams. 
20 
49.5 
50 
66 


Grams. 
43 

77 
70 
102 


Mm. 
45 

64 
67 
70 


Mvi. 
62 

75 
76 
80.5 


313 


Grams. 
70 
85.4 
95 
100 


Grams. 
101 
107 
132 
124 


Mm. 

74 
79 
72 
82 


Mm. 

83 


319 


287 


85 


299 


283 . . 


83 


341 


282.. 











Table 5. — Increase in One Year op Specimens prom Lot D, Weighing 

under 200 Grams. 





Wei 


ght. 


Length. 


Specimen No. 


Weight. 


Length. 


Specimen No. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 

1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


336 


Grams. 
120 
120 
125 
131 
134.5 


Grams. 
135 
147 
149 
160 
160 


M7n. 
79 
83 

83 
87 
89 


Mm. 

C) 
88 
86 
94 

(«) 


304 


Grams. 
145 
149 
163 

187 
195 


Grams. 
163 
172 
182 
222 
225 


Mm. 
89 
94 
91 
95 
99 


Mm. 
92 


317 


292... 




329 


331 




290 


310 . 




333 


339 . 


102 









a No record. 



14 



GEOWTH AND MIGRATION OF FEESH-WATER MUSSELS. 



Table 6. — Increase in One Year of Specimens from Lot B, Weighing 
OVER 200 Grams, Selected at Random from 20 Specimens One Year from 
Date of Planting. 





Weight. 


Length. 


Specimen No. 


Wei 


ght. 


Length. 


Specimen No. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


216 


Grams. 
193 
226.5 
240 
250 
25S.5 


Grams. 
215 
246 
263 

265 
270 


Mm. 
110 
101 
115 
110 
110 


Mm. 
Ill 
101 
116.5 
111 
111 


244 


Grams. 
282 
291 
308 
323.5 
378 


Grams. 
300 
302 
322 
335 
394 


Mm. 
114 
119 
114 
115 
119 


Mm. 
115 


239 


201 


120 


211 

251 


242 


1-14 


205 


116 


249 


120 









Table 7. — Increase in One Year of Specimens from Lot A, Weighing 
over 200 Grams, Selected at Random from 68 Specimens Reclaimed One 
Year prom Date of Planting. 





Weight. 


Lei] 


gth. 


Specimen No. 


Weight. 


Length. 


Specimen No. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


June, 
1910. 


June, 
1911. 


70 


Gram.t. 
199.5 
223.5 
240 
252 
256.5 


Grams. 
216 
235 
260 
270 
274 


Mm. 
96 
107 
106 

125 
106 


Mm. 
97 
108 
107 
125.5 
107 


9 


Grams. 
266.5 
270 
273.5 
316 
328 


Grams. 

277 
285 
304 
342 
340 


Mm. 
125 
114 
120 
120 
125 


Mm. 
125.5 


80 


5 


115 


10 


15 


120.5 


12 


2 


120+ 


I 


23 


125.5 











Averages for One Year. 



Table 4 
Table 5 
Table 6 
Table 7 



Average 
increase 
in weight. 



Grams. 
27.5 
24.55 
16.15 
17.75 



Average 
length. 



Mm. 
66.1 



112.7 
114.4 



in length, i^^'ength. 



Mm.. 
11.6 
3.5 



Per cent.a 

17.5 

3.9 

.7 

.6 



a Per cent of aggregate increase. 

The specimens under 100 grams make the largest increase in 
weight and length; those under 200 grams, the second; and those 
over 200, or fully mature specimens, fall short. A pomt of special 
mterest in connection with tables 6 and 7 hes in the fact that while 
per cent of gain in length is almost negligible, weight goes steadUy 
forward m fairly good proportion. From averages in tables 4 and 5, 
an average yearly growth for a young undulata (tlu-ee-ridge) might 
be put at 25 grams in weight and from 5 to 25 millimeters in length; 
at this rate it would take about eight years to reach the weight of 
200 grams and a length of 90 to 100 millimeters; as later growth is 
slower, about 12 to 15 years would be a fair estimate for the age of a 
Shoofly Creek undulata (three-ridge) of 300 grams in weight and 110 
to 120 millimeters in length. 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 
Table 8.— Rate of Growth by Species. 



15 



[Note.— This table shows species not mentioned in other tabulations, because the numberof individuals 
was too small for comparative study. The records are useful as indicative of what may beexpected from 
these species. The Quadrulse here listed are given because of their use in plate figures.] 



Speci- 
men 
No. 



109 
113 
111 
114 

281* 

564* 

413* 

430 

431 

XI 

X 

H* 

566* 
650 
495 
V 
LI 



Species. 



A. grandis (floater). 
...do 



.do. 
.do. 



Q. undulata (three-ridge). 



Q. lachrymosa (maple-leaf). 



.do. 



rV^Tien planted.. 

\1 year later 

/When planted.. 

U year later 

(Whenplanted.. 

\1 year later 

I TVlien planted.. 
U year later 

When plan ted.. 

1 year and 3 
months later. 

{'When plan ted.. 
1 year and 3 
months later. 
fMTienplanted.. 
\1 year later 

{When planted.. 
1 year and 3 
months later, 
r When planted . 

\1 year later 

When planted.. 
■\3 months later.. 
(When planted.. 
)3 months later.. 

(When planted-. 
1 year and 3 
months later. 
■UTien planted. . 
3 months later. . 
/When planted.. 

\ 1 year later 

i When planted.. 
\1 year later 

tetralasmus ^{Y^:^fl^^''^- 



T. tuberculata (buckhorn, pistol-grip).. 



.do. 



L. gracilis (paper-shell). 
....do 



.do. 



L. anodontoides (yellow sand-shell) 

....do 



.do. 



Time. 



j„ I When planted.. 
■ ™ \1 year later 



Weight. 


Length. 


Height. 


Grams. 


Mm. 


Mm. 


143 


120 


63 


193 


127 


66 


144 


120 


62 


192 


124 


65 


211 


132 


72 


269 


139 


74 


281.5 


140 


82 


320 


142 


82 


16.5 


40 


27 


51 


65 


41 


5 


22 


17 


20.5 


41 


32 


8 


27 


22 


18 


42 


35 


128 


87 


56 


138 


90 


68 


470 


136 


76 


489 


136.5 


76.5 


11 


51 


26 


29 


69 


35 


13 


55 


27 


55 


82 


44 


22.5 


63 


32 


84 


97 


50 


97 


93 


46 


116 


97.5 


49 


125 


103 


48 


138 


106 


49 


180 


110 


51 


186 


111 


51.5 


25 


65 


33 


30 


71 


36 


31 


70 


35 


43 


72 


37 



Breadth. 



Mm. 
41 
45 
41 
45 
48 
52 
53 
54 
16 
25 

10 
20 

13 
19 
31 
32 

50 
50 

14 

20.5 

18 

28 

19 

33 

34 

35.5 

37 

37.5 

43 

43 

20 

22 

22 

23 



DISCUSSION OF DATA. 

The results set forth iii the tables given above speak for them- 
selves and need no extensive explanation. 

One striking fact is the cessation of growth during the winter 
months of the Chikaskia specimens, especially in table 3. There are 
a number of cases in my field records where a loss is shown in we^ht 
for the six months from late September to early April, although in 
general they hold their own. It has been my observation for 
several years that the Chikaslda mussels, in the shallow water at least, 
burrow down mto the sand m late October and become abundant 
again in late AprU. 

For undulata (three-ridge), I have given rather complete averages 
of weight, and comparisons of rate of growth accordmg to size in 
tables 5-8. From tables 1 and 2 (all lot D), I find the averages given 
below for the four species named: Undulata (three-ridge), 12 speci- 
mens; lachrymosa (maple-leaf), 7 specimens; pustulosa (warty- 
back, pimple-back), 8 specimens; ruhiginosa, 5 specimens. From 



16 



GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 



table 8, grandis (floater), 4 specimens; tetralasmus, 2 specimens; 
gracilis (paper-shell), 2 specimens; anodontoides (yellow sand-shell), 
1 specimen. 

Average Increases in Weight and Length, by Species. 

AVERAGES FOR ONE YEAR. 



Species. 





Average 




Average 


increase 


Average 


weight. 


in 


length. 




weight. 




Grams. 


Grams. 


Mm. 


100 


30.8 


70 


'124 


28 


82 


74 


11.4 


68.8 


67 


11.5 


60 


194 


48.6 


128 


28 


8.5 


67 



Average 
Increase 

in 
length. 



Lachrymosa (maple-leaf) 

Unduiata (three-ridge) 

Rubiginosa 

Pustulosa (warty-back or pimple-back) . 

Grandis o (floater) 

Tetralasmus b 



Mm, 



l.h 

7.2 

3.4 

2.7 

5 

4 



AVERAGES FOR THREE SUMMER MONTHS. 



Gracilis (paper-shell) 

AnodontoidTes (yellow sand-shell) . 



22.5 
4.5 



o Large mature specimens, still the lncrea.se is good. 
b In an unusual environment lor this species (p. 9). 

Juvenile Quadrulae " of the above species double in size in a year, 
as shown by a number of examples (149, 158, 349, 323, in table 1; 
281, 564, 413, in table 8). Averages here given and those taken 
from other sources indicate that a 100-gram, 75-millimeter unduiata 
(three-ridge) (p. 14) or lachrymosa (maple-leaf) can develop in the 
Shoofly in about four years (averages for tables 1, 2, 4, and 5). A 
300-gram specimen of unduiata (three-ridge) or lachrymosa (maple- 
leaf) would doubtless be close to 15 years old. The largest unduiata 
(three-ridge) rechecked weighed 407 grams in June, 1910, and 421 
in June, 1911. This specimen was 123 millimeters long, and increased 
1 millimeter in length. In unduiata (three-ridge) and lachrymosa 
(maple-leaf), after the 100-millimeter length is reached, the increase 
in length is slow, and growth Imes follow one another so closely that 
the differentiation of lines is difficult. Pustulosa (warty-back, pimple- 
back) and rubiginosa grow more slowly than the two preceding species. 
A 50-millimeter 'pustulosa (warty-back, pimple-back) has passed the 
age of rapid growth, and from this size on additions come slowly. 

A light-shelled form, as L. gracilis (paper-shell) grows very rapidly; 
this would seem to indicate that the shell is built up at greater 
expense of food and energy than the soft parts of the mussel. In 
table 8, specimen X, during the three summer months, shows an 
increase of over four times in weight and 27 milUmeters in length; 
566, L. anodontoides (yellow sand-shell) , in the same time, makes an 
increase of one-fifth its original weight, and 4.5 millimeters increase 
in length. 



a Early juvenile forms grow even more rapidly as experimentally found (foot-note, p. 5) by Coker. 



GROWTH AND MIGEATION OF FRESH-WATER MUSSELS. 



17 



ARRESTED GROWTH RINGS. 



"Growth lines," the conspicuous dark concentric rings of the shell, 
may be due to (1) thick epidermis, (2) double epidermis, and espe- 
cially (3) to double epidermal and prismatic layers. It is well 
known that the epidermal and prismatic layers are formed by the 



.-"•'^ 






Fig. 1-4.— Cross-sect ions of shells of Q?;a(?rM?a showing structure inregion of rest rings, all figuresenlarged 
20 times; e, epidermis; p, prismaticlayer; n, nacreous layers; m', successive layers of nacreous structure; 
g, position and width of rest rings (growth lines). 

Fig. 1. — Section from near edge of shell, showing double layers and long underlying tongue of epidermal 
and prismatic structure, which formed the dark wide rest ring of a young rapid-growing Qua'^rula lachry- 
mosa. Rings 1 1 or i -, specimens 149 or 15S, plate n, would give similar sections. 

Fig. 2.— Section of shell of mature mussel, taken about the middle of the valve. Rest ring not so wide 
as in 1, tongue shorter, prismatic layer thicker, and thick successive layers of nacreous struciure. 

Fig. 3.— a rest ring due chiefly to unusually thick, double layers of epidermis. 

Fig. 4. — Two successive rest rings near together, undoubtedly formed in the same season, and probably 
only a few weeks apart, as specimen was young and at the rapid-growing age. (See description of specimen 
413, pi. n.) 

edge of the mantle only. Thus increase in shell diameter begins 
with the formation of the epidermal, followed by the prismatic layer. 
However, if the mantle is withdrawn from the edge of the shell, it 
often puts down new layers of epidermal and prismatic material 



18 GKOWTH AND MIGRATION OF FEESH-WATER MUSSELS. 

underneath older layers "^ of the same structure, and sometimes 
underneath older layers of nacre as well. This is well shown in 
figures 1-4, showing sections of shells made through the growth Imes. 

In watching the growth of tagged specimens it was noted that a 
distinct growth line was formed at the time of tagging; the work of 
tagging, i. e., the drilling of the hole through the shell and the placing 
of the wire, caused considerable irritation, probably a strong con- 
traction and partial breaking loose of the mantle from the edge of 
the shell, and, as a result, new epidermal and prismatic layers were 
put down underneath those already formed, as the mantle worked 
to its old position, and formed new layers over the wire holding the 
tag (pi. Ill, 763) . Young specimens, especially, show a conspicuous 
and well-defined ring passing through the outer side of the wire 
holding the tag. 

The so-caUed annual rings had better be called "arrested growth 
or rest rings," as they represent retarded growth, which may be 
very temporary, as in the case of the tagged specimens, and still 
leave a very marked ring. Ordinarily the prominent rest rings are 
presumably winter rings, ^ representing delayed growth, due to 
inactivity, a withdrawal of the mantle from the extreme edge of the 
valves, and the forming of double epidermal and prismatic layers 
as a result of renewed active growth in the following spring. Other 
rings may follow arrested growth, due to various unfavorable con- 
ditions that may arise in the life of the mussel, such as water 
shrinkage, temporary stranding due to migration, especially at flood 
periods; in the fighter species perhaps washing at flood times. It 
is possible that in certain pond forms, as V. tetralasmus and others 
that five in ponds that go dry for short periods during the summer 
season, the more prominent rings are summer rings.^ 

That the concentric rings are by no means dependable as abso- 
lute annual rings is well shown in many specimens under observation 
in this investigation. 

A few specimens shown photographically (pi. i, ii, iii) will clear 
up some points in regard to growth. Rest rings are not always 
brought out clearly by photographic methods on account of the 
unequal or convex surface of the sheU. A sfight ridge that may have 
no connection with a rest ring wiU show as a shadow line beyond 
the ridge. This is shown in photograph H, plate i, in the line 
marked "o." Additional explanations are given with the plate 
figures. 

a This explanation was first suggested to me by Dr. Coker, and later verified in connection with my 
study of shell sections through arrested growth lines. 

6 While in this paper we have emphasized the point that " annual rings ' ' are not annual rings absolutely, 
the statement that the prominent rest rings are usually, under stable enviromnental conditions, winter 
rings is clearly within the evidence of this investigation. 

e Live specimens of this species were plowed up in the Browne pond (p. 7) three months after the 
pond had gone dry. 



GROWTH AND MIGBATION OF FRESH-WATER MUSSELS. 19 

MIGRATION. 

No end of speculation has been carried on as to the traveling 
ability of mussels. The long undulation tracks, often found upon 
the pond or stream floor, together with other field observations, 
and the active movements of specimens kept in aquaria have afforded 
data for discussion. While gathering information concerning growth, 
I have constantly kept in mind the migration question, as it was 
easy to carry on the two together. 

As already indicated, the main reason for tagging a large number 
of mussels was the feeling that many would be lost through migration; 
and further to guard agamst this migration in the Chikaskia I inclosed 
the specimens in good-sized pens. 

SHOOFLY. 

The extent of actual ttiigration is best shown in considering definite 
plantings. Lot D (see p. 8) of the Shoofly is good for tliis purpose. 
The 168 Quadrulas planted here were from the Chikaskia, where 
they were collected from the sand bars in shallow water. From 
track-mark evidence these specimens had been actively moving 
about on the sandy bottom, stimulated to activity by unfavorable 
environmental conditions. 

The 164 specimens were spread out on a small portion of the 
bottom of the Shoofly (p. 8), June 16, 1910, and left free to move. 
June 14 and 15, 1911, I reclaimed 139 of these specimens, or 84.8 
per cent, in about three hours' work. Twelve of these specimens 
were reserved for records. On September 11, 1911, a cold rainy day, 
I again checked over lot D, and this time I secured 93 specimens in 
about one hour's time; the water was so cold that collecting was 
exceedingly difficult. Three specimens not found in June were 
found on this date, bringing the total number reclaimed from the 
original planting up to 142. When we consider that the water was 
cloudy and from 3 to 4 feet deep the experienced field collector wiU 
know that specimens could not be recovered in these numbers unless 
they were on the very spot ^ where they were planted. Lots A and 
B in the Shoofly gave similar results, although I did not attempt to 
recover these as thoroughly as in the case of lot D. 

Lot C in the Shoofly is of especial interest, as these specimens 
were all A. grandis (floater). Of this lot 12 specimens were found 
directly on the site where they were planted. Wliile this is rather 
a small per cent in comparison with lot D, I was surprised to find 46 
per cent of A. grandis (floater), as it is well known to be an active 

a It has been suggested that smce lot D specimens were transplanted the inactivity may have been due 
to the changed environment. The relatively rapid growth and Uke inactivity of lots A and B, Shoofly 
specimens, which might very well be considered as control lots, should quiet any apprehensions on this 
point. 



20 GROWTH AND MIGRATION OF FRESH-WATER MUSSELS. 

form. In all my reclaiming work in the Shoofly, which amounted 
to about 10 hours' actual hunting and collecting on three different 
days, I secured only one specimen that may be said to be off the 
planting plot; this was no. 141, found 15 feet from plot D. 

CHIKASKIA. 

In the Chikaskia lot E gave results similar to D. The Chikaskia 
Kiver specimens were disturbed somewhat by curious people, and for 
this reason proportional figures can not be emphasized. The inclosure 
for lot E (p. 9) was rather small, but there was ample chance for 
movement. The results in this instance substantiate what I have 
often noticed m field work, namely, that the mussels, especially 
Quadrulae and related species, are unable to help themselves if con- 
ditions become unfavorable, but, on the other hand, the power to 
endure these unfavorable conditions is remarkable. 

Since the Chikaskia is a fairly swift stream, the lower end of the 
inclosure was undermined, making escape easy, while a sand bar was 
formed across the upper portion. Two-thirds of the mussels were 
caught in the drift bar and when I examined them on September 26, 
1910, were helplessly stranded. Conditions of oxygen and food sup- 
ply must have been unfavorable, and as a direct result the summer's 
growth was below the average for lot F. 

These stranded specimens were now taken and put in the outer 
corner of the pen, where they could escape under the whe net through 
an opening 5 feet long. Six months later, June 22, 1911, I again 
examined lot E. A large number of the specimens were recovered, 
about half being along the wire net inside, and half along the net 
outside; not a specimen was found over 5 yards from the pen. 
Clear water and sandy bottom made the fhiding of specimens easy. 

Lot F spechnens of the Esch inclosure (p. 9) had a good opportu- 
nity for migration; in fact, the inclosure was not needed, as only 
two specimens reached either lower or upper cross fences. One of 
these was a gracilis (paper-shell), and the other a grandis (floater). 
The Quadrulae did not come within 25 yards of the lower fence. If 
they were placed m water over 3 feet deep, the migration was slight 
in any case, as far as the Quadrulae were concerned. Those placed in 
water as shallow as 1 foot moved to deeper water, which was easily 
reached in this case. The Lampsiles were more active, and the per- 
centage recovered was small by comparison. Of the 50 U. tetralas- 
mus, not a single specimen or shell was found at the first examination, 
September, 1910; but in the June, 1911, examination, three speci- 
mens were found. I am not able to explam the disappearance of the 
tetralasmus; however, they are great burro wers, and may have 
escaped my extensive digging for them. 



GBOWTH AND MIGRATION" OF FEESH-WATEB MUSSELS. 21 

DISCUSSION OF MIGRATION DATA. 

The migration results came as a surprise to me. The very fact 
that I was willing to risk specimens free in the Shoofly would indicate 
that I hoped to make some kind of recovery; but to go back and find 
specimens by the score — apparently in the exact spot where they were 
planted — was not to be expected. The Quadrulse m these plantings 
show little migration; the Shoofly specimens may be said to be nearly 
stationary in water over 3 feet deep. Those placed in shallow water 
in the Chikaskia always moved until water 2 to 3 feet deep was found. 
Specimens found on shoals and bars in nature are there by chance 
distribution, not choice, although breeding reactions may cause migra- 
tion m some species. 

ECONOMIC BEARING OF EXPERIMENTS— RELATED PROBLEMS. 

While the scientific interest in the growth and migration problems 
was the real motive that prompted this investigation, it was the 
relation of the problem to the practical question of artificial propa- 
gation of mussels for commercial purposes that made funds available 
to carry on the work. That the results will be of service as preluni- 
nary to further investigation is a matter of satisfaction. The man 
interested in commercial propagation will continue to ask the ques- 
tion, How long will it take to grow a mussel to marketable size? 
Much more work will be needed to get at all the facts in the case of 
the various economic species; and where the work of propagation is 
to be conducted on a large scale, preliminary experiments will be of 
value in testing the fitness of a particular region for commercial opera- 
tions. Some of the methods of procedure have been indicated by the 
series of experiments here ou timed. 

I wish to call the attention of the field students of the Unionidse 
to the transplanting of adult mussels from the Chikaskia to the Shoo- 
fly, where young specimens were not to be found, yet these trans- 
planted mussels averaged higher in rate of growth than the regular 
Chikaskia specimens. If the Shoofly is so favorable a habitat for 
mussels, why are young specimens absent from the beds ? 

Again, notice the transplanting of over a hundred specimens from 
the vicmity of lot F, where mussels are so abundant, to lot E : The 
transplanted specimens did as well in growth as the specimens that 
were near the region of abundant mussels in the Chikaskia. This 
difference in abundance was by no means slight. It is a fact that in 
the vicinity of lot F one could, in a few hours, collect a wagonload 
of mussels, while for a quarter of a mile above and below the Brewer 
inclosure two of us were able to get only 30 specimens in several 
hours' careful collectmg. 



22 GEOWTH AND MIGRATION OP FRESH-WATEE MUSSELS. 

The distribution of mussels within individual streams, and in the 
Chikaskia in particular, is not easy to explain. Little or negligible 
migration among the Quadrulse, at least, has not cleared the situation. 

SUMMARY. 

1. Rate of growth is exceedingly variable for individuals of a single 
species in the same stream and in different streams, depending, as in 
other invertebrates, upon season, food, oxygen supply, and other con- 
ditions. Juvenile mussels grow much more rapidly than adult or 
near-adult individuals. Lampsilis species grow very much faster 
than Quadrulse. Specimens in stable conditions seem to have a 
fairly definite rate of growth from year to year. The rate, after 
sexual maturity, is slowed down, but growth goes on steadily, though 
the proportional increase in length is so slow as to make appreciable 
additions very slight, so that growth lines in Quadrulse, after a size 
of 100 millimeters (4 inches) has been reached, can not be ascer- 
tained by inspection. 

2. From April to September may be designated as growth months, 
most specimens showing very slight increase during winter. 

3. Lmes of arrested growth may be called rest rings, the conspicu- 
ous ones being usually winter rest rings; very often, however, the 
rings may be two or more years apart, or several equally prominent 
rings may be formed in one year. Prominent lines are generally due 
to double prismatic and double epidermal layers. Winter rings, es- 
pecially where environmental conditions are stable, are usually suffi- 
ciently regular for use as indicators of age in estimating roughly the 
time required for a commercial species to reach marketable size. 

4. Under favorable conditions there is little migration among the 
Quadrulae. Some of the Lampsiles and other light-shelled species 
move about quite actively, but probably seldom migrate far from the 
point where they were dropped from the fish, although their total wan- 
derings may be considerable. Water of sufficient depth is essential 
to optimum conditions. The minimum depth seems to be at least 2 
feet; the range up to the maximum has not been studied. Quadrulse 
prefer water over 2 feet deep. The reason they are found on the 
shoals in many of our streams may be explained as chance distribu- 
tion, due probably to the fact that the particular individuals have 
never found optimum conditions after their parasitic development, 
and the reason they move about is that they do not find the right 

environment. 

LITERATURE CITED. « 

CoKER, R. E., and Surber, T. 

1911. A note on the metamorphosis of the mussel Lampsilis Isevissimus. Bio- 
logical Bulletin of the Marine Biological Laboratory, Woods Hole, Mass., 
vol. 20, p. 179-182, 1 pi. 

a Dr. A. E. Ortmann and Dr. F. Haas have called my attention to Dr. Haas's monograph, "Die Union- 
idae in Martini-Chemnitches Conchyliencabinet," 1910. I have not had access to this paper. 



GROWTH AND MIGRATION OF 



'ATER MUSSELS. 



23 



ISELY, F. B. 

1911. Preliminary note on the ecology of t^ 
Ibid., vol. XX, p. 77-80. 
Israel, W. 

1909. tJber die Najadeen des Mittelelbeg^ 

Gesellschaft von Freunden der 
p. 1-38. 

1910. Die Najadeen des Weidagebeites. 

poisclien Najaden. Beilage zumj 
zoologischen Gesellschaft, p. 49-56 

1911. Najadologische Miscellen. NachricJ 

gischen Gesellschaft, p. 10-17. 
Lefevre, G., and Curtis, W. C. 

1908. Experiments in the artificial prop| 

ceedings of the Fourth Internat 

Bulletin of the Bureau of Fisherij 
1910a. Reproduction and parasitism in the 

Zoology, vol. 9, p. 79-115, 5 pi. 
1910b. Studies on the reproduction and art 

sels. Bulletin of the Bureau of 

VI-XVII. 

EXPLANATION Ot 

All photographs are about natural size. Fc 
already explained (pp. 10, 11, and 15), tags 
wire passed through a small hole made about 
ally along the edge of the posterior umboidal 
the ring formed when the specimen was 
formed without exception in all specimens h^ 
the mussel at the time of tagging and making 
natural processes between tagging time and 
due to a ridge on the valve and in photograpl 

Plate I 3 

Specimen H, Lampsilis gracilis (table 8), sho'v 
(June, 1910, to Sept., 1911); x marks the rest' 
marked and measured; a;' is probably the 1910-11^ 

Specimen 323, Quadrula undiilata (table 1), sli 
growth (June, 1910, to June, 1911). A new ring.; 
the two rings, y^ and y'^, near together, formed 

Specimen 281, Quadrula undulata (table 8)| 
(June, 1910, to Sept., 1911); x^ is probably the 

Plate I] 

Specimen 355, Quadrula rubiginosa (table 
(June, 1910, to Sept., 1911) in a mature slow- 
rings beyond x. 

Specimen 349, Quadrula pu^tulosa (table 1 
(June, 1910, to June, 1911). , A rest ring, not 
shows very near the margin; o, on the anteriori 

Specimen 564, Quadrula lachrymosa (table 8 
15 months (June, 1910, to Sept., 1911). Tagpul! 

Specimen 413 (table 8), shows 16 mm. incr| 
1911). Two rest rings, x^, x^, in addition to the 
If we count the one at the tagging line we have t3ii 



livenile life of the Unionidae. 



jl u. 52. Jahresberichte der 
bnschaften in Gera, Reuss., 

ir Kenntniss der Mitteleuro- 
sblatt der deutschen malako- 

ler deutschen malakozoolo- 



fresh-water mussels. Pro- 
lery Congress (Washington), 
cvui, p. 617-626. 

Journal of Experimental 

Jpagation of fresh-water mus- 
vol. XXX, p. 105-201, pi. 

is. 

leasurements see tables. As 

led on with a small copper 

the edge of the shell, usu- 

larks the tagging ring, i. e., 

measured. This ring was 

thus marks the diameter of 

3rds; x', rest rings formed by 

[ot specimen; o, shadow line 

• be mistaken for a rest ring. 



rowth in length in 15 months 
led when the specimen was 
Br rest ring; o, shadow line. 
"17 mm. increase in one year's 
jt z' near the margin. Notice 
specimen was tagged. 

mm. growth in 15 months 
fcst ring. 



mm. increase in 15 months 
jecies. No evidence of rest 

lO mm. increase in one year 
^ght out by the plate figure, 

shadow line. 
[9 mm. increase in length in 
ifter specimen was reclaimed, 
year (June, 1910, to June, 
BJIformed at the time of tagging, 
rest rings for one year. 



24 



GEOWTH AND 



)N OF FEESH-WATER MUSSELS. 



Specimens 149 and 158, Quaa 
thirds natural size). These apf 
from the Chikaskia. The rest ri 
1910, to June, 1911) is the same. 

Specimen 158 is the left Aalvji 



Specimen 566, Lampsilis cnoc 
nearly three months (Jun 
men growing in rather uiifci 

Specimen 763, Quadrula lad 
(t) nearly three months after [ 

Specimen 200, Quadrula 
193 grams was found in Jun( 
be called young. No. 200 if 
larity of rest rings, four in ni 
according to estimates workec 
was 4 or 5 years old when tal 



ichrymosa (table 1 and as shown here about two- • 

are from the Shoofly, the two lachrymosa above ■ 

are about the same as 413 and the time (June, , 

80 does not show the tag or mark. f 

^Plate III. ii 

ft'.s (table 8) , shows 5 mm. increase in length in i 
lo Sept. 19, 1910). A mature Chikaskia speci- ■ 
feViAdronment. 

hows how the tag wire is overlaid with nacre ; 
[^une 27, 1910, to Sept. 19, 1910). 

In the Shoofly (p. 7) no Q. undulata under i 
in 1911 two specimens were secured that may 
ese and is interesting on account of the regu- ' 
he specimen measures 80 mm. in length and, , 
n kno'H'n growth of this fspecies in the Shoofly, , 



o 









,31 ^-,.- - 



U. S. B. F.— Doc. 792 



Plate I. 




SPECIMEN Hi' 




SPECIMEN 281. 



U. S. B. F Doc. 792. 



Plate II. 





SPECIMEN 355. 



SPECIMEN 349. 





SPECIMEN 149. 



SPECIMEN 564. 





SPECIMEN 158. 



SPECIMEN 413. 



U. S. B. F.— Doc. 792. 



Plate III. 




SPECIMEN 566. 




SPECIMEN 763. 




SPECIMEN 200. 



LIBRARY OF CONGRESS 



002 903 626 3 



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